Uh-oh! We ran into a hiccup when trying to start the Local Machine
Address already in use
On the Mac, in Terminal, a list of open files using TCP showed the application that was using the port that Local needed:
sudo lsof -i -n -P | grep TCP
It showed that the port was in use by my VPN.
I disconnected the VPN and Local started up OK. The VPN re-connected, evidently picking a different port.